PORTSMOUTH — Police say a spilled drink on the dance floor was the motive behind an attack at a Portsmouth bar over the weekend that potentially led to the victim's death.

According to court documents, 24-year-old Zachary O'Neill, of Dover, told workers at The Page Restaurant & Bar he assaulted another patron Saturday morning because the man spilled a drink on him several hours earlier.

The victim, 24-year-old Joshua Krantz, was then hit from behind while he was dancing on the lower level of business. Witnesses said O'Neill repeatedly punched him in the head after he hit the ground. Krantz declined medical treatment and returned home to his apartment in Dover, where he was found dead several hours later.

O'Neill was arraigned Wednesday morning on a first-degree assault charge. He entered no plea while appearing in Portsmouth Circuit Court at about 9 a.m. The medical examiner's office has yet to rule on whether Krantz's death was a homicide — a determination that would prompt police to elevate the charge.

A Portsmouth police prosecutor requested O'Neill be held on $250,000 cash only bail, citing his criminal record, as well as a history of failing to appear in court.

Prosecutor David Colby said O'Neill was also “dishonest” this week with investigators, who were led to believe he would surrender himself into police custody. When he failed to do so, Portsmouth police issued a “be on the lookout” notice Tuesday. O'Neill was arrested later in the evening at a family member's home in Rochester.

Colby also recounted a January 2012 incident in which O'Neill was charged with disorderly conduct by Portsmouth police. An officer was forced to pull O'Neill off another man during a fight at the High-Hanover parking garage at 1:05 a.m., Colby said.

O'Neill failed to appear in court to answer to the charge on separate occasions in September and October 2012. He then skipped a trial date last Tuesday, April 2, leading the court to issue a bench warrant for his arrest.

“We do feel that he's a danger to the community,” Colby said.

This weekend's attack at The Page happened at 12:44 a.m., shortly before closing time. Police say O'Neill told bar staff he waited to hit Krantz until then because he knew he would get thrown out of the business and “didn't want to ruin his night.”

O'Neill was asked to leave, and the bar did not report the incident to police. He later bragged about punching Krantz and demonstrated the manner of the assault, an acquaintance told investigators.

One woman who was interviewed by police said she was present at the bar with O'Neill on Saturday, and witnessed the incident involving the spilled drink. The woman said she watched O'Neill punch Krantz in the head repeatedly later in the evening. He then called her after the incident using a friend's phone to apologize, the witness told police.

An independent witness reported seeing O'Neill deliver a “haymaker” to the victim, punching him in the back of the head behind the ear.

Krantz later complained of nausea and a severe headache, and covered his head with a jacket when he arrived back home in Dover, according to his roommates.

Krantz eventually told friends he was OK and went to sleep. His roommate then heard him snoring louder than usual around 3 a.m. and shook him, according to a police affidavit. Krantz was found unresponsive the next morning, covered in “vomitous material,” the affidavit states.

Dover police were called to his apartment to investigate the unattended death at about 11:30 a.m. A state medical examiner in Concord later determined that Krantz died of a fractured skull, leading to an “epidural hematoma.”

O'Neill was taken into custody on Saturday by Dover police. He admitted to being at The Page overnight, then declined to answer questions about the fight and asked for an attorney.

Police executed a search warrant Sunday at O'Neill's apartment at 12 New York St. While the search was under way, O'Neill allegedly told the officers who were present from Dover and Portsmouth: “I don't see what the big deal is ... it was just a bar fight ...” or words to that effect.

O'Neill spoke only a few sentences in court Wednesday. At one point, he attempted to clarify for the judge that two men — not one — were involved in the street fight last January in Portsmouth.

“I believe there was two defendants in which I engaged physically in the parking lot,” he said.

O'Neill also entered a plea of not guilty Wednesday on a separate misdemeanor charge alleging he violated bail orders issued in Strafford County by committing the assault over the weekend. The case stemmed from a Feb. 4, 2013, traffic stop in Dover. He faces charges of driving with a suspended license (a subsequent offense), carrying a loaded firearm in the car without a permit and possessing an undisclosed quantity of marijuana.

Judge Sawako T. Gardner ordered O'Neill held on $250,000 cash bail. He was ordered to have no contact with the Krantz family, employees at The Page, four other men and one woman.